Shielded plot sprayer

ABSTRACT

A mobile shielded plot sprayer including a wind shield having a side wall that defines an enclosed area, and a movable atomizer within the enclosed area. A track assembly is located within the enclosed area and supported on the windshield. The atomizer is part of a spray assembly mounted on the track assembly and is movable thereon in at least one horizontal direction relative to the wind shield. A reservoir integral with the spray assembly and adapted to hold a liquid spray composition is operatively connected to the atomizer to supply the spray composition thereto.

This Application is a Divisional of application Ser. No. 09/405,695filed Sep. 24, 1999 now U.S. Pat. No. 6,390,387 which claims the benefitof U.S. Provisional Application Ser. No. 60/101,965 filed Sep. 26, 1998.

FIELD OF THE INVENTION

This invention generally relates to agricultural field sprayingequipment, and more particularly to a plot sprayer useful in fieldresearch relating to biological effectiveness of agricultural chemicalson crops and weeds.

BACKGROUND OF THE INVENTION

Agricultural chemicals, including pesticides, plant growth regulators,foliar fertilizers, desiccants and the like, are typically applied toplants or soil by spraying using various types and designs of mobilespraying equipment. The agricultural chemicals are normally diluted,dissolved or dispersed in a suitable liquid carrier, most commonlywater, to form a composition that is suitable for spraying and isreferred to herein as a “spray composition”. The application rate of asprayed chemical can be metered by controlling four factors: the rate oftravel of the spraying equipment over the ground, the rate at which thespray solution is dispensed, the width of the swath being sprayed, andthe concentration of the chemical in the spray solution.

Rate of travel of the spraying equipment, expressed, for example, inmeters per second (m/s), is dictated by forward speed during spraying,whether motion is imparted by human power, as in the case of hand-heldor backpack-mounted spraying equipment, or by mechanical power, as inthe case of tractor-mounted spray equipment or purpose-built motorizedspray rigs.

Rate of dispensing, or output, of the spray solution, expressed, forexample, in liters per second (l/s), is dictated by several factors: thenumber of simultaneously operating spray nozzles, the configuration, inparticular the size of the orifice of each nozzle, the propulsion forceapplied (normally provided by hydraulic pressure), and the rheologicalproperties of the spray solution, especially its viscosity. The term“nozzle” in the present context is to be understood to apply to anyatomization means having the function of a nozzle. Similarly, the term“orifice” in the present context is to be understood to apply to thefeature or part of any atomization means having the same function as theorifice of a nozzle.

Spray swath width, expressed, for example, in meters (m), is dictated bythe number of nozzles arranged on a boom disposed perpendicularly to thedirection of travel of the spray equipment, the distance betweennozzles, the angular width of the conical or fan-shaped spray patterngenerated by the orifice of each nozzle, the degree of overlap ofadjacent spray patterns, and the height of the nozzles above the groundor plant target.

Concentration of the chemical in the spray solution, expressed forexample in grams/liter (g/l), is controlled by the operator duringpreparation of the spray solution, most commonly by mixing a measuredamount of a concentrate formulation having a known concentration of thechemical in a measured volume of water.

Chemical application rate is the product of the above parameters and canbe expressed as

R=OC/TW

where R is chemical application rate, O is spray solution output, C isconcentration of chemical in the spray solution, T is speed of forwardtravel and W is swath width. When T is expressed in m/s, W in m, O in1/s and C in g/l, R is given in grams per square meter (g/m²).

Modern spray equipment can generally be fairly precisely calibrated withrespect to the above parameters to deliver a desired chemicalapplication rate. Under ideal weather conditions, such calibration leadsto an actual application rate which is more or less constant andreproducible and which varies little (typically +/−10% or less) from thedesired rate.

However, weather conditions are seldom ideal. In particular, wind, evena light wind, disturbs the spray pattern sufficiently to compromiseaccuracy and precision of a well calibrated sprayer. When wind speed anddirection vary constantly, a condition known as turbulence, this problemis still more acute. Turbulent air movement frequently occurs nearground level even when air movement a few meters above ground isnon-turbulent. This turbulence is often further aggravated by motion ofthe spray equipment.

An additional source of variation in application rate, even when asprayer is perfectly calibrated, is vertical movement or oscillation ofthe spray boom or nozzle caused by travel over an irregular groundsurface by a wheeled vehicle carrying the spraying equipment. Suchvertical movement can be a problem also with hand-held spray equipmenteven when operated by an experienced technician walking on level ground.As the spray boom or nozzle is raised or lowered, spray swath width andthe degree of overlap of adjacent spray patterns vary, resulting inirregularities in deposition of the spray composition.

Yet another problem is disturbance of soil or plants immediately before,during or immediately after spraying by the moving wheels of a vehicleor the walking feet of an operator carrying the spraying equipment. Suchdisturbance can take the form, for example, of local compaction of thesurface layers of soil, leading to variation in the effectiveness ofsoil-applied chemicals. Disturbance of plants can affect theirbiological response to an applied chemical as well as result inaccidental transfer of an applied chemical to other plants.

A particularly high degree of accuracy, precision and reproducibility isrequired when the chemical application is for research purposes.Agricultural researchers must be able to precisely evaluate the effectsof particular rates of a chemical on crop and/or weed plants occupying aparticular area of a field demarcated for such evaluation. Such ademarcated area is referred to herein as a plot. Typically, researcherscompare the performance of plants in a sprayed plot to that in a nearbyor adjacent unsprayed control plot. Generally, several differentchemical treatments are compared, each treatment being applied to adifferent plot. It is important, therefore, that the chemical isprecisely dispensed only on the intended plot, and uniformly within thatplot, with little or no wind-assisted drift of the spray solution on toadjacent plots.

The occurrence of wind is, in most climates, very frequent. If sprayinghas to be restricted to periods of relative calm, the number of plotsthat can be sprayed in a season is limited. Research productivitysuffers as spray operators are often unable to apply chemicals at theoptimum time, because of windy weather. Thus, a need exists in the artfor a spraying apparatus which is able to accurately dispense a chemicalwithin a plot with minimum effects from wind and turbulence. Such anapparatus would greatly improve research productivity as well asaccuracy.

As spraying can seldom wait until conditions are absolutely calm,researchers have to some extent adapted their procedures to allow for atleast a light wind. For example, it is common to leave buffer stripsbetween plots to avoid wind-assisted drift from one plot contaminatingadjacent plots. The need for buffer strips increases the amount of landneeded for field testing of agricultural chemicals, or reduces thenumber of treatments that can be accommodated in a single experiment. Asthe experimental area becomes larger, variability in soil and plantconditions increases, tending to reduce the precision of the experiment.A further benefit of a windproof spraying apparatus would therefore beto reduce the amount of land required for a field experiment and therebyto improve the precision of such an experiment.

Previous attempts to provide spraying equipment with wind protectionhave involved partially or totally surrounding a spray boom, orindividual spray nozzles on a boom, with a shield or skirt which iscarried on the boom. Shielded sprayers of this type do reducewind-assisted drift of spray solution, and can also be used to protectplants sensitive to a chemical from spray application of the chemicalclose to such plants (for example, in selective application of aherbicide to weeds between the rows of a crop). However, a new problemis introduced which is of particular relevance in research plots. Theshield or skirt tends to become coated with the chemical and transferschemical to plants as it passes over them. Further, the spray solutiondrips from the bottom edge of the shield or skirt. In these and otherways, shielded sprayers of prior art contribute to inaccuracy ofapplication.

There is a long-standing need for improved spraying apparatus that canprecisely apply an agricultural chemical treatment to a plot in variablewind conditions, and that minimizes the need for buffer strips betweenplots. An improved spraying apparatus that meets this need, and at thesame time eliminates vertical movement or oscillation of the spray boomor nozzle would be a particularly useful advance in the art. An improvedspraying apparatus that has these benefits, and that in operation causesno disturbance of soil or plants other than the direct effects ofspraying, would be an even more useful advance in the art. It is justsuch an improved spraying apparatus that is now provided.

SUMMARY OF THE INVENTION

The present invention relates to a spray apparatus for spraying a plotof land with a liquid spray composition. The spray apparatus is readilyrelocatable without disassembly and comprises (1) a rigid frame; (2) awind shield, supported on or integral with the frame, comprising a sidewall that defines an enclosed area and has a top edge that is preferablysubstantially horizontal and is located at a suitable height; (3) atrack assembly located within the enclosed area and supported on theframe; (4) a spray assembly mounted on the track assembly and movablethereon in at least one horizontal direction relative to the windshield, the spray assembly comprising atomizing means located at aheight lower than any substantial part of the top edge of the side wall;(5) a permanent or replaceable reservoir external to or integral withthe spray assembly, adapted to hold a liquid spray composition andoperatively connected to the atomizing means to supply the spraycomposition thereto; (6) means for transmission of power to the sprayassembly for movement thereof on the track assembly; (7) drive controlmeans, to permit operator control of said movement of the sprayassembly; (8) fluid propulsion means, i.e., means for causing the spraycomposition to flow from the reservoir through the atomizing means, toeffect spraying; (9) flow control means, to permit operator control ofspraying; and (10) means for moving the apparatus vertically andhorizontally, such that the apparatus is readily relocatable withoutdisassembly.

By “readily relocatable” it is meant that the entire apparatus can betransported laterally from one plot to another in a field by a smallnumber of persons acting together, or with the aid of conventional farmmachinery. The frame is of such construction, and the other componentsof the apparatus are disposed with respect to the frame in such amanner, as to permit easy relocation of the entire apparatus withoutdisassembly. Means for moving the apparatus vertically and horizontallycan take a number of forms. For example, the frame can be provided withoptionally retractable wheels, to enable the apparatus to be movedlaterally from one plot to another. Preferably, however, the frame isprovided with lifting means, to facilitate raising of the entireapparatus off the ground at the location of a first plot, transportingof the apparatus to the location of a second plot, and lowering of theapparatus on to the ground at the location of the second plot. Suchlifting means can be, for example, a plurality of handles to permitraising, transporting and lowering by two or more persons. In preferredembodiments, the lifting means are hitching means, by which theapparatus can be hitched to a tractor or other powered vehicle capableof raising, transporting and lowering the apparatus. Such hitching meanstypically comprise a plurality of hitching points and can be adapted,for example, for connection to a conventional tractor-mountedthree-point hitch or fork-lift device.

The side wall of the wind shield preferably comprises four substantiallyrectangular side panels that are substantially vertical and areconnected to each other at approximately 90° angles. The side panels canbe of substantially equal length so as to define a square enclosed area;however for most applications it is preferred that there be a longerpair and a shorter pair of opposing side panels, thereby defining asubstantially rectangular enclosed area. The wind shield preferablyfurther comprises a substantially horizontal, square or rectangular topcanopy which is connected to the side wall, for example at or close tothe top edge thereof, so as to leave substantially no gaps between thetop canopy and the side panels.

In one embodiment the side panels, and optionally the top canopy, are ofrigid construction and have sufficient mechanical strength and rigidityto serve both as the wind shield and as the frame. In this embodiment,therefore, the wind shield is integral with the frame. However, for mostpurposes it is preferred that the wind shield and frame are notintegral, and that the side panels and top canopy are constructed of alightweight material attached directly to the frame. It is especiallypreferred that this material be transparent, to permit operation of thespray assembly within the enclosed area to be visually monitored by aperson standing outside the wind shield.

It is also preferred that at least one of the side panels or the topcanopy be provided with an aperture large enough to permit insertion,removal or servicing of a reservoir. This aperture facilitatesreplacement or refilling of the reservoir after a plot has been sprayedand the spray apparatus has been, or is about to be, moved to anotherplot.

The track assembly, in one embodiment of the invention, comprises asingle fixed horizontal track, typically oriented parallel to the longerpair of side panels and midway between them. On such a track the sprayassembly is movable in one direction only. In another embodiment of theinvention, the track assembly comprises a first track mounted fixedly onthe rigid frame and a second track mounted movably on the first track,both of these tracks being located within the enclosed area. The firstand second tracks are oriented perpendicularly to each other, the firsttrack being typically oriented parallel to the longer pair of sidepanels and midway between them. In this embodiment, the spray assemblyis movably mounted on the second track. The first and second tracks aremovably connected by a carriage. This arrangement allows the sprayassembly to be moved across a plot in any desired pattern, for examplein a scan pattern that includes a series of parallel passes.

The spray assembly comprises atomizing means which is preferably ahydraulic nozzle or a plurality of such nozzles. In an embodiment of theinvention having a single fixed track on which the spray assembly ismounted, a preferred spray assembly comprises a boom orientedperpendicularly to the track, with a plurality of nozzles mounted atsubstantially regular intervals along the boom. The boom supports thenozzles and forms or carries a portion of a conduit through which aliquid spray composition can flow from the reservoir to all of thenozzles.

In a particularly preferred embodiment having only one nozzle, the sprayassembly is movable horizontally in a first direction and a seconddirection perpendicular to the first direction so as to be capable ofuniformly spraying the entire enclosed area. This is preferablyaccomplished using a track assembly comprising two perpendicular tracksas described above, wherein the second track is mounted movably on thefirst track and the spray assembly is mounted movably on the secondtrack. Most preferably in this embodiment, the reservoir is integralwith the spray assembly, i.e., is part of the spray assembly itselfrather than being located elsewhere in the apparatus, and is connectedto the nozzle by a rigid coupling piece having an internal conduitthrough which the spray composition is fed from the reservoir to thenozzle. This coupling piece can incorporate a quick-release coupling topermit easy replacement of the reservoir with minimal spillage of unusedspray composition.

Drive means to cause the spray assembly to move on the track assembly(including, in an embodiment with two perpendicular tracks, drive meansto cause the carriage carrying the second track to move on the firsttrack) can be internal to the spray apparatus but is preferablyexternal, the spray apparatus itself having an operative connection tosuch external drive means. For example, the external drive means cancomprise an electric power generator and the operative connection cancomprise a power cable that leads to an electric motor forming part ofthe track assembly and providing motive force to propel the sprayassembly. As another example, the external drive means can comprise asource of hydraulic power and the operative connection can comprise asystem of pipes providing hydraulic pressure to propel the sprayassembly. In the embodiment described above wherein the track assemblycomprises perpendicular first and second tracks movably connected by acarriage, an operative connection to drive means is provided both to thecarriage, permitting movement of the second track on the first track,and to the spray assembly, permitting its movement on the second track.

Drive control means can comprise electrical switches and/or hydraulicvalves, operatively connected to a control panel. The drive controlmeans can be automated to varying degrees; in a preferred embodiment allaspects of motion and operation of the spray assembly, includingspraying, are programmably controlled by a computer.

Fluid propulsion means, to cause the liquid spray composition to flowfrom the reservoir through the atomizing means, can be internal to thespray apparatus or external thereto. Flow can occur by gravity feed, forexample to a spinning disk atomizer which draws the spray compositionthrough at a constant rate, controllable by the speed of rotation of thespinning disk. Electrical power to drive a spinning disk can be providedfrom an external source (e.g., a generator) or a source located withinthe apparatus (e.g. a battery pack). Preferably, however, the fluidpropulsion means is hydraulic pressure provided by pressurized gas, inwhich case the preferred atomizing means is a hydraulic nozzle orplurality of such nozzles. Pressurized gas, for example carbon dioxide,nitrogen, air or propane, can be supplied from a bottle. Alternatively,it can be supplied directly from a compressor. In either case thepressurized gas is supplied to the reservoir by an airline running fromthe source of pressurized gas to the reservoir. The term “airline” asused herein means a conduit for pressurized gas not restricted tocompressed air.

Flow control means typically comprises one or more valves in the airlineand/or in a conduit through which the spray composition flows from thereservoir to the atomizing means. Such valves can be designed for manualoperation or can be computer controlled. In the embodiment describedabove wherein the track assembly comprises perpendicular first andsecond tracks movably connected by a carriage, the flow control meanscan be configured to cause spraying to occur when the spray assembly isin motion in a first direction parallel to the first track, and toprevent spraying when the spray assembly is stationary or in motion in asecond direction parallel to the second track.

The present invention also relates to a process for spraying a plotusing a spray apparatus as described herein. This process comprises thesteps of (1) positioning the apparatus in a field such that the enclosedarea defined by the wind shield covers the plot; (2) adding a suitablequantity of a spray composition to a permanent reservoir, or coupling areplaceable reservoir containing a spray composition to a spray assemblyadapted to receive such a replaceable reservoir; and thereafter (3)operating, or causing a computer control system to operate, a switch orplurality of switches to cause the spray assembly to move in apredetermined pattern across the plot and to spray the spray compositionuniformly over the entire plot. Steps (1) and (2) of this process can becarried out in either order.

The spray apparatus of the invention is particularly adapted forconsecutively spraying a plurality of plots, for example inimplementation of an agricultural chemical field trial. Accordingly, aprocess is provided for consecutively spraying a plurality of plotsusing a spray apparatus as described herein, comprising carrying outsteps (1), (2) and (3) as described above; followed by (4) releasingunused spray composition from a permanent reservoir and rinsing thereservoir, or uncoupling a replaceable reservoir from the sprayassembly; and (5) repeating steps (1) to (4) with further spraycompositions on second and subsequent plots until all plots have beensprayed.

The present invention overcomes the problems of prior art sprayers byproviding an easily relocatable, lightweight enclosure which isstationary during operation and a spray assembly for spraying a liquidspray composition within the area defined by the enclosure, which cancorrespond to the area of a plot. The apparatus of the present inventionprovides more accurate application of spray compositions to plots, andmore uniform application across a single plot than prior sprayequipment. The improved accuracy and uniformity can result fromelimination of wind and turbulence, or from absence of vertical movementor oscillation of the spray assembly, or both. The apparatus alsoeliminates disturbance of soil or plants within plots by wheel-trackingor trampling. The present invention in one embodiment also permits rapidapplication of numerous spray compositions consecutively to differentplots, without the risk of contamination of one spray composition byremnants of a previously applied spray composition in the apparatus.Because of these and other advantages, agricultural researchers canapply spray compositions to test plots more rapidly and accurately thanin the past, and this can improve the speed, accuracy and productivityof their research.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a spray apparatus according to theinvention, mounted illustratively on a farm tractor.

FIG. 2 is a perspective view of a wind shield in accordance with theinvention.

FIG. 3 is a perspective view of a rigid frame, a wind shield and a sprayassembly movably mounted on a track assembly located inside an enclosedarea defined by side panels of the wind shield.

FIG. 4 is a perspective view of a track assembly and a spray assembly inaccordance with the invention.

FIG. 5 is an overhead view of an area enclosed by the wind shield of aspray apparatus of the invention, the enclosed area comprising a plot tobe sprayed.

FIG. 6 is a cutaway perspective view of an alternative embodiment of aspray apparatus having a wind shield that serves also as a rigid framein accordance with the invention.

FIG. 7 is an end elevational view of a first track and carriage of aspray apparatus in accordance with the invention.

FIG. 8 is a perspective view of a wind shield having mounted thereon anexternal rack of spray bottles (replaceable reservoirs) in accordancewith an embodiment of the invention.

FIG. 9 is a side elevational view of a spray assembly of one embodimentof the invention.

FIG. 10 is a side elevational view of an improved spray assembly inaccordance with a preferred embodiment of the invention.

FIG. 11 is an exploded view of part of the spray assembly of FIG. 10.

FIG. 12 is a schematic diagram of the operating system of a sprayapparatus of the invention.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention provides a field plot spraying apparatus that isparticularly suited for agricultural research purposes. The apparatusincludes a wind shield which during spraying is stationary relative to aplot of land, and provides an enclosed area around that plot, and aspray assembly that moves within the enclosed area and relative to thewind shield so that a liquid spray composition can be applied to all orpart of the plot. The wind shield is mounted on a rigid frame and thewhole apparatus is readily relocatable from one plot to another withoutdisassembly.

One embodiment of the wind shield and frame is shown in FIG. 1. The windshield 22 is attached to and substantially covers the frame 20 which iscapable of supporting the entire weight of the apparatus. The frame canbe hitched to a vehicle such as a farm tractor 12 by means, for example,of a standard three-point hitch (obscured in FIG. 1 by the rear tire 14of the tractor). The three-point hitch can be used to lift the apparatusoff the ground and hold it in an elevated position while the tractordrives to a different location, carrying the apparatus along with it.When the tractor arrives at the new location, the apparatus can belowered., again by means of the three-point hitch, so that bottomhorizontal members 34 a-34 d of the frame 20 rest on the ground.Although the apparatus of the present invention could be used forspraying while the bottom horizontal members 34 a-34 d are lifted offthe ground, it is preferred to spray with the lower edge of the windshield 22, which in this embodiment is contiguous with the bottomhorizontal members 34 a-34 d of the frame 20, touching the ground inorder to minimize wind-induced distortion of spray patterns.

The apparatus could be moved by other means, such as a fork lift, ormanual lifting by several people. However, it will usually be mostefficient to lift, lower, and move the wind shield with a farm tractoras in FIG. 1 or a functionally equivalent vehicle such as a truck. Thetractor can also provide electrical or hydraulic power for moving thespray assembly (described below) within the enclosure defined by thewind shield, and/or for compressing gas to pressurize the reservoircontaining the liquid composition to be sprayed.

The wind shield 22, shown without the tractor in FIG. 2, is preferablyconstructed of a flexible material securely attached to the frame 20.The wind shield 22 of FIG. 2 has a side wall comprising four side panels24 a-24 d and a top canopy 26. The side panels 24 a-24 d and the topcanopy 26 are preferably rectangular and joined to each other at 90°angles. The side panels 24 a-24 d and top canopy 26 define an enclosedarea. The horizontal dimensions of the area enclosed by the wind shield22 are preferably either equal to the size of the plot to be sprayed orsomewhat larger than the plot in order to allow a buffer zone at theedges of the enclosed area.

Horizontal dimensions of the enclosed area, and hence of a plot forwhich the apparatus is a useful spraying device, are not narrowlylimited. For example, an enclosed area having length and breadth each ofabout 1 to about 10 m can readily be provided. Illustratively, a lengthof about 5 m and breadth of about 2.5 m have been found to beconvenient. Height of the top canopy, or of the top edge of the sidepanels in the absence of a top canopy, is likewise not narrowly limited.the primary requirement being that the spray apparatus can beaccommodated such that the atomizing means is at a suitable height forspraying while at the same time no higher than the top edge of the sidepanels. Where a top canopy is present, the entire spray assembly istypically below the top canopy. These considerations normally dictate aminimum height above ground (when the apparatus is in position forspraying) of the top canopy or of the top edge of the side panels ofabout 0.5 m, but for most applications a minimum height of about 1 m ismore appropriate. Apparatus of the invention can be purpose-designed fora wide variety of situations. including for use in tall-growing crops orother vegetation, thus the top canopy or the top edge of the side panelscan be up to about 3 m, or even more, above ground. For use on bare soilor low-growing crops or weeds, it is more convenient for the height ofthe top canopy or the top edge of the side panels to be no more thanabout 2 m.

The frame 20 is rigid and preferably made of a lightweight material suchas aluminum or fiberglass. The frame can comprise a plurality ofindividual structural members that are rigidly connected, for example bybolts or welds. Suitable materials for the wind shield 22 includecanvas, woven polypropylene and polyethylene film. It is preferred forthis material to be transparent in order to allow observers to visuallymonitor the spray operation within the enclosed area defined by the windshield.

It will be appreciated that since the spraying apparatus is designed tobe frequently moved to different plot areas, it needs to be anchored tothe ground only sufficiently to prevent toppling or dislodgement by windor other lateral forces. It will also be appreciated that many differentanchoring methods can be employed, including relying on the weight ofthe apparatus itself in low wind conditions. In high wind conditions,supplemental weights could be hung on the frame 20, or anchoring pegscould be driven into the ground and the frame 20 secured to such pegs.

In another embodiment of the invention, a wind shield 10 is provided inthe form of a rigid four-sided box, as shown in FIG. 6, in which casethe wind shield can function also as the frame on which other parts ofthe apparatus are supported and to which a tractor or other vehicle canbe hitched. In this embodiment, the wind shield 10 can suitably includerigid side panels 74 and a rigid top canopy 72.

FIG. 3 shows a wind shield 22 constructed of transparent material,together with frame 20 and some of the internal components of thespraying apparatus. The specific embodiment shown in this figureincludes hooks 28 as alternative means for grasping and lifting the windshield. However, as explained above, it is usually preferable to connectthe frame 20 to a standard hitch such as a three-point hitch on a farmtractor (linkage not shown in FIG. 3). The frame 20 in this embodimentincludes corner vertical members 30 a-30 d, top horizontal members 32a-32 d, bottom horizontal members 34 a-34 d, and top struts 36 toprovide additional rigidity to the structure.

Where the track assembly comprises a single track, this track ispreferably medianly situated in the enclosed area and oriented parallelto the longer rather than the shorter sides of the wind shield. It canconveniently be attached, for example by bolts or welds, to the tophorizontal members 32 a and 32 c and to the top struts 36 of the frame20. The single track can comprise two parallel rails that can be engagedby wheels of the spray assembly, and a rigid support gantry whichensures the rails do not move relative to one another, potentiallycausing derailment or jamming of the spray assembly.

In the specific embodiment illustrated in FIG. 3, the track assemblycomprises a first, or X-axis, track 42 medianly and fixedly mounted onthe frame 20 and a second, or Y-axis, track 40 movably mounted on theX-axis track 42 and oriented perpendicularly thereto. This Y-axis trackcomprises a bar 50 having mounted movably thereon a spray assembly 45.The spray assembly includes a mounting bracket 46, a nozzle 47 and areservoir 48.

Turning to FIG. 4, which shows the Y-axis track 40 and the X-axis track42 without showing the frame 20, the mounting bracket 46 is in thisembodiment movably mounted on the underside of the bar 50 of the Y-axistrack 40, so that the spray assembly 45, which includes the mountingbracket 46, nozzle 47 and reservoir 48, can be moved back and forth inthe second direction, or Y-axis, within the area enclosed by the windshield. Preferably this is accomplished by including a pair of rails onthe underside of bar 50, with wheels (not shown) rotatably mounted atthe top of the mounting bracket 46 movable on those rails. Pressureapplied within the reservoir 48 causes a liquid spray compositiontherein to be emitted from the nozzle 47 in a spray pattern 52downwardly on to soil or plants.

The X-axis track 42 of the embodiment illustrated in FIG. 4 includes asupport gantry 54 which is fixedly attached to the frame 20 (not shown),for example by welds or bolts. Thus, in operation, the X-axis trackremains stationary relative to the frame and wind shield. The supportgantry 54 can optionally have support struts (not shown) to providefurther rigidity. The X-axis track 42 also includes a pair of rails 56which are fixedly mounted on the support gantry 54, at least at each endand preferably also at a plurality of points along their length. Therails 56 provide a path for wheels 58 which are rotatably mounted on acarriage 60 that is in turn fixedly attached to the Y-axis track 40,thereby permitting the Y-axis track 40 to move back and forth in thefirst direction, or X-axis. In this manner the spray assembly 45 can bemoved in both the X- and Y-axes within the enclosure defined by the windshield.

An example of a suitable path for the movement of a single-nozzle sprayassembly, in an embodiment of the invention having X-axis and Y-axistracks, is shown in the overhead view of FIG. 5. A plot 62 to be sprayedis shown by the diagonal shading. The area 64 enclosed by the windshield 22 is in this illustrative case larger than the plot, andincludes additional end regions 65 and 66, one on each end of the plot62. Within the area enclosed by the wind shield 22. the spray assemblyis moved in a scan pattern that includes a series of parallel passes.For example, the spray assembly begins at the location marked bycoordinates X₀, Y₀. When operation on a plot commences, the sprayassembly is first moved by drive means on the Y-axis track to coedinatesX₀, Y₁. Next, the Y-axis track carrying the spray assembly is move bydrive means on the X-axis track, so that the spray assembly proceedsfirst to coordinates X₁, Y₁ at the opposite end of the plot 62. Thespray assembly then moves on the Y-axis track to coordinates X₂, Y₂before proceeding to coordinates X₁, Y₂ by movement of the Y-axis trackon the X-axis track as before, but in the reverse direction. Bycontinuing this scan pattern across the plot as indicated by arrows 67a-67 d, and by activating the spray assembly during the time it ispassing over the plot in the X-axis, the entire plot 62 is sprayed.After the scan pattern is completed, the spray assembly returns to thestart coordinates (X₀, Y₀). Table 1 gives a suitable example of thesequence of moves for the spray assembly.

TABLE 1 Move X location Y location start X₀ Y₀  1 X₀ Y₁  2 X₁ Y₁  3 X₂Y₁  4 X₂ Y₂  5 X₁ Y₂  6 X₁ Y₃  7 X₂ Y₃  8 X₂ Y₄  9 X₁ Y₄ 10 X₁ Y₀ 11 X₀Y₀

Note that the spray assembly continues in the X-axis direction past theends of the plot 62. In one method of operation, spraying continuesthroughout the entire travel time in the X-axis, thereby also sprayingportions of end regions 65 and 66 to form buffer zones 68. In anothermethod of operation, spraying is automatically started and stoppedduring travel in the X-axis so that only the plot 62 itself is spray.With either method of operation, as a result of this extended travelbeyond the limits of the plot 62, the buffer zones 68 provide foracceleration and deceleration of the spray assembly. Thus, during thetime the spray assembly is traveling in the X-axis over the plot 62 itis moving at substantially constant velocity across the plot, therebyenhancing uniformity of the rate of application of the spraycomposition.

As an example of suitable dimensions, the plot 62 can be 144 inches(3.66 m) long in the X-axis and 96 inches (2.44 m) wide in the Y-axis,the area 64 enclosed by the wind shield 22 can be 216 inches (5.49 m)long and 96 inches (2.44 m) wide, each buffer zone 68 can be 18 inches(0.46 m) long and 96 inches (2.44 m) wide, the length 70 of sprayassembly travel in the X-axis can be 180 inches (4.57 m), the distance71 between the long side panel 69 of the wind shield 22 and the line ofthe first pass 67 a in the X-axis of the spray assembly can be 12 inches(0.30 m), and the distance between consecutive passes, for example 67 aand 67 b, in the X-axis can be 24 inches (0.61 m). This is consistentwith the entire width of the plot being sprayed with non-overlappingspray patterns in consecutive passes, and with a spray pattern width of24 inches (0.61 m).

In a preferred embodiment, the spray apparatus is arranged to spray onlywhile the spray assembly is moving in the X-axis. In other words, in theparticular embodiment illustrated in FIG. 5, while the spray assemblymoves along segments 67 a-67 d of the scan pattern, an open valve (notshown) permits spraying to occur. At or before the moment when the sprayassembly reaches the end of such a segment and starts to move in theY-axis, the valve closes to stop spraying. The valve limiting sprayingto the time when the spray assembly is traveling in the X-axis can betriggered by any suitable switching device located on the X-axis track,or can be set to open automatically when travel begins on a segment 67a-67 d of the scan pattern and close automatically when travel iscompleted on such a seginent. The valve itself can be in an airlineproviding pressure to the reservoir, or in the conduit for the spraycomposition leading from the reservoir to the nozzle of the sprayassembly.

Drive means for moving the spray assembly 45 on the Y-axis track 40 anddrive means for moving the Y-axis track on the X-axis track 42 can eachtake a number of forms. For example, an electric motor can be used tocause a chain or pulley to draw the carriage 60, which carries theY-axis track 40, along the X-axis track 42, as shown in FIG. 7. Thepreferred drive means is a hydraulic or oil pressure operated system ofa kind well known in the agricultural machinery art, which providesseveral desired characteristics. For instance, such a system provides aconsistent controllable velocity. The system also provides forconsistent, repeatable and accurate stops of the spray assembly. Inaddition, the system provides for high rates of acceleration anddeceleration to maximize the portion of the total travel path of thespray assembly within which velocity is substantially constant.

Whether operated hydraulically or electrically, it is preferred thatoperation of the sprayer be robotic or controlled electronically, forexample by means of a programmable computer. Control systems for thetypes of motion described herein are commercially available, as arecontrol panels suitable for the present apparatus.

For an apparatus of the invention having a single track, drive means formovement of the spray assembly on the track can be as described abovefor movement of the carriage on the X-axis track.

FIG. 12 shows, in schematic form, an operating system suitable for aspray apparatus of the invention. External drive means 121, which canbe, for example, an electric generator or storage battery, or ahydraulic power generating system, provides power for movement ofcarriage 124 on the track assembly (not shown). Power is supplied fromdrive means 121 to carriage 124 by transmission means 122, which in thecase of hydraulic power typically comprises a hydraulic pipe systemcontaining oil, and in the case of electric power typically compriseselectric cable connected to an electric motor situated in or on carriage124. Transmission means 122 is provided with drive control means 123,which can comprise one or more valves or switches and is, in a preferredembodiment, operated by electronic signals transmitted along cable 133from computer 132.

Also shown in FIG. 12 is the fluid propulsion means, typicallycomprising an external pressurizing means 125, such as a compressor orpre-pressurized gas cylinder, which feeds pressurized gas throughairline 126 to reservoir 128 of the spray assembly. The pressurized gaspropels a spray composition from reservoir 128 through conduit 129 toatomizing means 130, from which the spray composition emerges as a spray131. A flow control means is provided in the form of controllable valve127 located at a convenient point in airline 126; alternatively orsupplementarily a flow control means is provided in the form of acontrollable valve or shut-off in conduit 129 (not shown). The flowcontrol means is, in a preferred embodiment, operated by electronicsignals transmitted along cable 134 from computer 132.

In an agricultural research setting it is often useful to apply numerousspray compositions, each to a separate plot, so that the effects of thecompositions on plants, or on plant diseases, pests or pathogens, can becompared. In order to facilitate the application of many spraycompositions one after another to successive plots with minimum loss oftime between applications and with minimum opportunity for error, theapparatus of the present invention can include a spray bottle rack. Asshown in FIG. 8, in one embodiment the frame 20 has mounted on it anexternal rack 80 which can hold numerous spray bottles 82, eachcontaining a liquid spray composition in an amount designed forapplication to a single entire plot. The rack is preferably positionedat the end of the apparatus proximal to the tractor, close to theoperating controls for maximum convenience and efficiency of operation.Preferably the spray bottles form replaceable reservoirs 48 (of FIG. 6),but in an alternative embodiment the contents of each spray bottle arepoured or drawn into a permanent reservoir.

A side panel 24 of the wind shield 10 preferably contains an aperture 84to allow an operator to manually remove a spray bottle from the sprayassembly inside the wind shield 10, select a new spray bottle 82 fromthe rack 80, insert the new bottle through the aperture 84, and connectthe new bottle to the spray assembly. Most preferably, the aperture 84is closeable, for example by means of a flap. Thus, a different spraycomposition can be applied to each plot on which the apparatus issuccessively placed, and a large number of plots can be sprayed in quicksuccession with a high degree of precision.

FIG. 9 shows a portion of a spray assembly 88 of one embodiment of theinvention in which pressurized gas, for example carbon dioxide at about28 psig (193 kPa), is supplied from an airline 89 through a bottomfitting 92 attached to a coupling piece 91 into which the neck of thespray bottle 90 can be inserted and held in position, for example by aconventional screw fitting. The pressurized gas passes from the bottomfitting 92 through the coupling piece up into the upper part of thespray bottle or reservoir 90 via a tube 94, and forces the liquid spraycomposition out through a conduit in the coupling piece into ahorizontal spray boom 96 attached to the coupling piece. From the sprayboom 96 the liquid spray composition is released through one or moredownward pointing nozzles 98. A valve 100 can be used to permit or stopflow of the spray composition into the boom 96.

One disadvantage of the spray assembly of FIG. 9 is that after thereservoir 90 is emptied, some of the spray composition will remain inthe boom 96. If not completely ejected from the spray nozzles and boom,this remaining spray composition will contaminate the next spraycomposition used, and therefore may render the results of an experimentinaccurate (for example by causing a plot to receive a mixture of afirst herbicide composition and a second herbicide composition when theresearcher intended that plot to be treated only with the secondherbicide composition).

FIG. 10 shows a portion of an improved spray assembly 88 for use in apreferred embodiment of the present invention. A female quick-connectfitting 102 extending to one side of a coupling piece 106 is adapted toreceive pressurized gas from an airline such as a hose connected to agas bottle, air compressor or other source (not shown). The pressurizedgas passes into a tube 104 which carries the gas through the couplingpiece 106 to the upper part of the spray bottle or reservoir 101. Thegas pressure within the reservoir 101 forces the liquid spraycomposition contained therein down through the coupling piece 106 and anozzle 108 attached directly to the bottom of the coupling piece. Thenozzle atomizes the liquid spray composition and creates adownwardly-directed spray pattern 52. Each spray bottle on the rack 80shown in FIG. 8 preferably comprises all of the assembly shown in FIG.10. Therefore, when a first spray composition has been applied to afirst plot from a first spray bottle, the spray apparatus can then belifted and moved to a second plot, the first spray bottle can bemanually removed by releasing the quick-connect fitting 102 from theairline, a second spray bottle containing a second spray composition canbe selected from the rack 80, and it can then be attached to theairline, again by means of quick-connect fitting 102, so that the secondspray composition can then be applied to the second plot.

The preferred embodiment of spray bottle 82 is shown in an exploded viewin FIG. 11. In this view, the various components of nozzle 108 are shownas cap 110, seal gasket 112, spray tip 114, ball valve strainer 116, andnozzle body 118. The various components of nozzle 108 are commerciallyavailable, for example from Spraying Systems Co. of Wheaton, Ill.

Although in preferred embodiments the spray composition reservoir takesthe form of a replaceable spray bottle such as that illustrated in FIG.10 and is mounted integrally on the spray assembly as described above,the spray composition could alternatively be stored in a permanentreservoir not part of the spray assembly itself. For instance, thereservoir could be mounted in a fixed position, for example on the frame20, and be connected to the spray assembly by a flexible conduit so thata connection is maintained during the entire travel of the sprayassembly within the enclosure defined by wind shield 10.

Use of the shielded plot sprayer of the present invention has proved tobe a significantly improved method of spraying research field plots bycomparison with conventional prior art methods. One major advantage isimproved precision of evaluation of biological effectiveness of testcompositions on a variety of plant species. This improved precisiontakes the form of reduced variability in data derived from differenttest plots receiving the same treatment.

To illustrate this advantage of the invention, a field test wasimplemented on a farm in Illinois. Several annual broadleaf and grassspecies were planted in rows and were permitted to grow to a suitableplant growth stage for treatment with the post-emergence foliar appliedherbicide glyphosate. Sufficiently uniform populations of six of thesespecies established for evaluation of the herbicidal effectiveness ofglyphosate. The six species were velvetleaf (Abutilon theophrasti,ABUTH), morningglory (Ipomoea sp., IPOSS), prickly sida (Sida spinosa,SIDSP), common waterhemp (Amaranthus radis, ANIATA), spring wheat(Triticuin aestivum, TRZAS) and barnyardgrass (Echinochloa crus-galli,ECHCG). Plots were marked off in such a way that each plot extended overrows of all six species.

Eight herbicidal treatments were applied, one to a plot, in a replicatedblock experimental design with three replications of each treatment. Aset of plots was left untreated as a control. The eight treatmentsconsisted of applications of two commercial isopropylammonium glyphosateformulations, ACCORD® herbicide and ROUNDUP® ULTRA herbicide, both ofMonsanto Company, each at four rates (0.14, 0.28, 0.56 and 1.12kilograms glyphosate acid equivalent per hectare). ROUNDUP® ULTRAcontains a surfactant and is designed to be used alone; ACCORD®herbicide contains no surfactant and is generally used with addition ofa surfactant adjuvant in the spray tank. In the present study, however,no surfactant was added. All applications were made in a water volume of93 liters per hectare.

The entire study was done four times in separate runs, with all runsbeing made concurrently one afternoon in August. At the time ofspraying, air temperature was 23° C., relative humidity 75% and a lightwind was blowing from a north-northwesterly direction at 11 km/h. Thiswindspeed is not normally considered excessive for conducting fieldspray trials. In one run of the study, a spray apparatus of theinvention, as illustrated in FIGS. 1, 3, 4, 6, 7, 8, 10 and 11 anddescribed in passages of text herein referring to these Figures, wasused for all treatments. In the other three runs, the treatments wereapplied by hand-held boom sprayers operated by three different fieldresearch technicians, all very experienced in conducting field testssuch as the present study, and referred to herein as applicators 1, 2and 3.

Twenty-six days after treatment (DAT), percent inhibition of all sixspecies in all plots was evaluated independently by two experiencedfield research technicians. Percent inhibition is a visual measurementof herbicidal effectiveness by comparison with untreated plots, whereina percent inhibition of 0% indicates no effect and a percent inhibitionof 100% indicates that all plants of a particular species in a plot werecompletely dead. A percent inhibition of 85% or more is in most casesconsidered acceptable for commercial herbicide use.

Thus the data set gathered from this study includes a total of 288 datapoints (8 treatments×3 replicates×2 evaluators×6 species) for each ofthe four runs, one of which is illustrative of the present invention andthe other three are illustrative of a standard method in the art. Thedata from each of the four runs were subjected to a separate analysis ofvariance. It is generally recognized in the art that analysis ofvariance of field data of the type generated in this study is ofdoubtful value as a means of establishing significance of differencesamong treatments, unless the data are subjected to an appropriatestatistical transformation. This is because towards the top of thepercent inhibition range, i.e., near 100%, within-treatment variancesare normally much smaller than those in the middle or near the bottom ofthe range. For example, a highly effective herbicide treatment appliedto a species in three replicate plots might give percent inhibition dataof 92%, 95% and 97% respectively, while in the same field test a lesseffective treatment might give percent inhibition data of 40%, 60% and72% respectively. “Least significant differences” established byanalysis of variance of such data could lead to misleading conclusions,underestimating the significance of small differences in the commercial(≧85% inhibition) part of the range and overestimating the significanceof larger differences in the middle or lower part of the range.

For the present purpose, however, analysis of variance was conducted notto attempt to discern differences among treatments but to establish theerror variance in each of the four runs of the test. As the spread ofdata was similar in all four runs, no serious misinterpretation resultsfrom analysis of the untransformed data; therefore no transformation wasdone. “Error variance” as used herein is the mean square for error,derived from the error sum of squares divided by the number of degreesof freedom for error, in the present case 30. A large value of errorvariance indicates a high degree of variability from plot to plot withintreatments; progressively lesser degrees of variability are indicated byvalues of error variance tending towards zero.

Table 2 shows the mean percent inhibition for all eight treatments ineach run of the test, together with the error variance applying to thatrun.

TABLE 2 percent inhibition, 26 DAT ABUTH IPOSS SIDSP AMATA TRZAS ECHCGaverage shielded sprayer of mean 60.92 47.85 64.67 79.35 95.31 86.94 theinvention error variance 54.33 192.17 106.25 113.40 20.75 36.87 87.30hand-held sprayer mean 66.19 48.63 64.60 69.69 96.52 88.29(applicator 1) error variance 104.24 209.09 109.43 109.14 14.80 44.9598.61 hand-held sprayer mean 60.25 45.35 57.17 63.29 95.96 86.27(applicator 2) error variance 53.18 238.16 155.44 140.46 25.55 57.75111.76 hand-held sprayer mean 74.79 54.50 69.81 78.79 95.42 89.40(applicator 3) error variance 88.70 275.16 177.65 114.61 47.08 77.68130.15

It will be noted that use of the shielded sprayer of the inventionprovided the lowest error variance of the four runs of the test forthree of the six species (IPOSS, SIDSP and ECHCG). For ABUTH, theshielded sprayer of the invention provided close to the lowest errorvariance; only applicator 2 gave marginally lower but applicators 1 and3 gave much higher error variance. For AMATA, the shielded sprayer ofthe invention gave the second lowest error variance in the study,applicator 1 giving the lowest and applicator 3 coming close to matchingthe error variance of the shielded sprayer. For TRZAS, the shieldedsprayer again came second to applicator 1, but both applicators 2 and 3gave higher error variance. The average error variance across all sixspecies shows the shielded sprayer of the invention clearly to givelower overall error variance than any of applicators 1, 2 or 3 usingstandard hand-held spraying equipment.

The above study illustrates a surprising advantage of use of the presentapparatus over a conventional method of field plot spraying, under lightwind conditions normally considered acceptable for such conventionalmethod. The benefit of using the present apparatus will be considerablygreater under more windy or turbulent conditions.

As a further illustration of the usefulness of the present apparatus, ashielded sprayer similar to that used in the study described immediatelyabove has been used to conduct a field experiment involving sprayapplication of a ¹⁴C-radiolabelled herbicide to plants to measure uptakeand translocation of the herbicide. In addition to the advantages of theapparatus in enhancing accuracy and uniformity of spray application, theenclosure formed by the wind shield ensures containment of theradiolabelled material and permits effective decontamination.

The preceding description of specific embodiments of the presentinvention is not intended to be a complete list of every possibleembodiment of the invention. Persons skilled in this field willrecognize that modifications can be made to the specific embodimentsdescribed here that would be within the scope of the present invention.

What is claimed is:
 1. A process for spraying a plot with a liquid spraycomposition, comprising the steps of: (1) positioning in a field amobile shielded plot sprayer having a wind shield, a spray assembly anda permanent resevoir, such that the enclosed area defined by the windshield of said sprayer covers the plot; (2) adding a suitable quantityof a spray composition to the reservoir; and thereafter (3) initiatingoperation of the spray assembly of said sprayer to move in apredetermined pattern across the plot and to spray the spray compositionuniformly over the entire plot; wherein steps (1) and (2) of saidprocess are carried out in either order.
 2. A process as set forth inclaim 1 for consecutively spraying a plurality of plots with liquidspray compositions, further comprising the steps of: (4) releasingunused spray composition from the reservoir and rinsing the reservoir;and (5) repeating steps (1) to (4) on second and subsequent plots untilall plots have been sprayed.
 3. A method as set forth in claim 1 whereinthe spray assembly includes a single spray nozzle, and wherein said stepof initiating operation of the spray assembly comprises moving thesingle spray nozzle in a pattern over the plot.
 4. A process forspraying a plot with a liquid spray composition, comprising the stepsof: (1) positioning in a field a mobile shielded plot sprayer having awind shield and a spray assembly adapted to receive a replaceablereservoir, such that the enclosed area defined by the wind shield ofsaid sprayer covers the plot; (2) coupling a replaceable reservoircontaining a spray composition to the spray assembly of said sprayer;and thereafter (3) initiating operation of said spray assembly to movein a predetermined pattern across the plot and to spray the spraycomposition uniformly over the entire plot; wherein steps (1) and (2) ofsaid process are carried out in either order.
 5. A process as set forthin claim 4 further comprising the step of: (4) uncoupling thereplaceable reservoir from the spray assembly and removing the reservoirfrom said enclosed area through an aperture in the wind shield.
 6. Amethod as set forth in claim 4 wherein the spray assembly includes asingle spray nozzle, and wherein said step of initiating operation ofthe spray assembly comprises moving the single spray nozzle in a patternover the plot.
 7. A method of applying a liquid spray composition to atleast one plot using a mobile plot sprayer, the method comprising thesteps of: moving a mobile wind shield to a location over said one plotsuch that the plot is at least partially shielded from the wind;delivering liquid spray composition from a reservoir having an outletlocated within the wind shield to a spray assembly of the mobile plotsprayer located within the wind shield; and moving the spray assembly ina pattern within the wind shield over the plot while spraying liquidcomposition.
 8. A method as set forth in claim 7 further comprising thestep of moving the reservoir outlet with the spray assembly in said stepof moving the spray assembly in a pattern.
 9. A method as set forth inclaim 8 wherein the step of moving the reservoir outlet comprises movingthe reservoir with the spray assembly.
 10. A method as set forth inclaim 7 wherein the mobile plot sprayer includes a frame supporting thewind shield, and wherein said step of delivering liquid spraycomposition comprises withdrawing liquid spray composition from thereservoir supported by a mobile plot sprayer frame.
 11. A method as setforth in claim 10 wherein said step of delivering liquid spraycomposition comprises withdrawing liquid spray composition from thereservoir mounted on the spray assembly for movement therewith.
 12. Amethod as set forth in claim 10 further comprising the steps of removingthe reservoir from the mobile plot sprayer and replacing the reservoirwith a new reservoir.
 13. A method as set forth in claim 12 wherein saidstep of removing the reservoir includes passing the reservoir and thenew reservoir through an aperture in the windshield.
 14. A method as setforth in claim 7 wherein said step of moving the spray assemblycomprises the step of initiating operation of a computer programdirecting movement of the spray assembly over the plot.
 15. A method asset forth in claim 7 wherein said step of moving the spray assemblycomprises moving a second track along a first track supporting thesecond track within the wind shield and moving the spray assembly alongthe second track.
 16. A method as set forth in claim 7 wherein said stepof moving the spray assembly comprises moving the spray assemblyexclusively within a single plane.
 17. A process for spraying a plotwith a liquid spray composition, comprising the steps of: (1)positioning in a field a mobile shielded plot sprayer having a sprayassembly adapted to receive a replaceable reservoir, such that theenclosed area defined by the wind shield of said sprayer covers theplot; (2) coupling a replaceable reservoir containing a spraycomposition to the spray assembly of said sprayer; and thereafter (3)initiating operation of said spray assembly to move in a predeterminedpattern across the plot and to spray the spray composition uniformlyover the entire plot; (4) uncoupling the replaceable reservoir from thespray assembly and removing the reservoir from said enclosed areathrough an aperture in the wind shield. wherein steps (1) and (2) ofsaid process are carried out in either order.
 18. A method of applying aliquid spray composition to at least one plot using a mobile plotsprayer, the method comprising the steps of: moving a mobile wind shieldto a location over said one plot such that the plot is at leastpartially shielded from the wind; delivering liquid spray compositionfrom a reservoir having an outlet located within the wind shield to aspray assembly of the mobile plot sprayer located within the windshield; and moving the spray assembly in a pattern within the windshield over the plot while spraying liquid composition, including movingthe reservoir and reservoir outlet with the spray assembly.
 19. A methodof applying a liquid spray composition to at least one plot using amobile plot sprayer including a frame supporting a wind shield, themethod comprising the steps of: moving the mobile wind shield to alocation over said one plot such that the plot is at least partiallyshielded from the wind; delivering liquid spray composition from areservoir having an outlet located within the wind shield to a sprayassembly of the mobile plot sprayer located within the wind shield; andmoving the spray assembly in a pattern within the wind shield over theplot while spraying liquid composition said step of delivering liquidspray composition comprises withdrawing liquid spray composition fromthe reservoir supported by the mobile plot sprayer frame for movementtherewith.
 20. A method of applying a liquid spray composition to atleast one plot using a mobile plot sprayer including a frame supportinga wind shield, the method comprising the steps of: moving the mobilewind shield to a location over said one plot such that the plot is atleast partially shielded from the wind; delivering liquid spraycomposition from a reservoir supported by a mobile plot sprayer frame,the reservoir having an outlet located within the wind shield to a sprayassembly of the mobile plot sprayer located within the wind shield;moving the spray assembly in a pattern within the wind shield over theplot while spraying liquid composition; removing the reservoir from themobile plot sprayer and replacing the reservoir with a new reservoir,including passing the reservoir and the new reservoir through anaperture in the wind shield.
 21. A method of applying a liquid spraycomposition to at least one plot using a mobile plot sprayer, the methodcomprising the steps of: moving a mobile wind shield to a location oversaid one plot such that the plot is at least partially shielded from thewind; delivering liquid spray composition from a reservoir having anoutlet located within the wind shield to a spray assembly of the mobileplot sprayer located within the wind shield; and moving the sprayassembly in a pattern within the wind shield over the plot whilespraying liquid composition, said step of moving the spray assemblycomprising moving a second track along a first track supporting thesecond track within the wind shield and moving the spray assembly alongthe second track.
 22. A method of applying a liquid spray composition toat least one plot using a mobile plot sprayer, the method comprising thesteps of: mounting a reservoir of liquid spray composition on a sprayassembly of the mobile plot sprayer; moving the mobile plot sprayer to alocation over said one plot; delivering liquid spray composition from areservoir to the spray assembly for spraying such that the liquid spraycomposition travels only a short distance before being sprayed out ofthe spray assembly.
 23. A method of applying a liquid spray compositionas set forth in claim 22 wherein the reservoir is located within a windshield of the mobile plot sprayer as mounted on the spray assembly. 24.A method of applying a liquid spray composition to at least one plotusing a mobile plot sprayer, the method comprising the steps of: movinga mobile wind shield to a location over said one plot such that the plotis at least partially shielded from the wind; delivering liquid spraycomposition from a reservoir having an outlet located within the windshield to a spray assembly of the mobile plot sprayer located within thewind shield; moving the spray assembly in a pattern within the windshield over the plot while spraying liquid composition; and moving thereservoir outlet with the spray assembly in said step of moving thespray assembly in a pattern.
 25. A method of applying a liquid spraycomposition to at least one plot using a mobile plot sprayer, the methodcomprising the steps of: mounting a reservoir of liquid spraycomposition on a spray assembly of the mobile plot sprayer such that thereservoir is located within a wind shield of the mobile plot sprayer;moving the mobile plot sprayer to a location over said one plot;delivering liquid spray composition from a reservoir to the sprayassembly for spraying such that the liquid spray composition travelsonly a short distance before being sprayed out of the spray assembly.